1. Held of the Invention
The invention relates to a method of processing a metal wire rod using an emulsion lubricant and a purification system for purifying the emulsion lubricant.
2. Description of the Related Art
Emulsion lubricants are used for e.g. wire drawing of metal wire rods such as copper wire rods.
In general, the emulsion lubricants are formed of a mixture of oil (mineral oil or plant oil) for improving lubricity, a surfactant for dispersing oil into water as well as for providing an effect of cleaning a workpiece, and water. In the emulsion lubricants, oil droplets are finely dispersed in the water by the surfactant.
Contaminants such as a metal powder (e.g., copper powder) produced during processing increase in the emulsion lubricant according as the operating time elapses.
Since the increased contaminants such as metal powder in the emulsion lubricant cause a problem of flaws on the processed surface of the metal wire rod, the emulsion lubricant is purified by removing the contaminants before being used again (see JP-A-2001-170708, JP-A-2008-142746 and JP-A-2011-218426).
JP-A-2001-170708 discloses a method of removing scale from a rolling lubricating oil, in which the first step is settling and removal of metal mill scale which is likely to settle out in an auxiliary tank and the following second step is removal of fine metal mill scale by filtration.
JP-A-2008-142746 discloses a method of drawing a metal wire rod, in which insoluble accumulated unwanted substances (particles of more than 20 μm in size) in an emulsion lubricating liquid is removed by centrifugation with a gravitational acceleration of not less than 30 G and not more than 150 G using a centrifuge and then the emulsion lubricating liquid is returned to a lubricating liquid tank and is reused for the wire drawing process. According to the invention of JP-A-2008-142746, it is possible to prevent separation of water and oil in the lubricating liquid.
JP-A-2011-218426 discloses a lubricating oil purifier which is provided with a centrifuge for removing contaminants in a collected used lubricating oil and a filtration system for removing contaminants present in the lubricating oil after passing though the centrifuge.